If It's Out, Call It Out!

So this just happened to me in a recent doubles match - in the middle of a point, I was on the ad side and my partner was on the deuce side and both of us were back around the baseline. I was close to mid-court and hit a forehand down the line that hit the outside line of the doubles alley (as I saw it) and angled away from my opponent. She reached for the ball but missed. She then said, "I wasn't really looking at the ball so I can't say if it was in or out. Can we replay the point?"
Now you and I know that, once my opponent expressed any doubt at all about calling the ball in or out, the point was mine. Because if you can't positively say that a ball was out, then it was in and (in the above situation) you lose the point.
How do we know this? Well, let's start with ITF Rule of Tennis 12 which states:

If a ball touches a line, it is regarded as touching the court bounded by that line.

Seems pretty clear. But the USTA has added their own Comment 12.1 to this rule which further explains:

If a player cannot call a ball out with certainty, should the player regard the ball as good? Yes. The Code sec. 6 and sec. 8 require a player to give the opponent the benefit of any doubt.

So let's look at The Code - The Player's Guide for Matches When Officials are not Present. Section 6 states:

6. Opponent gets benefit of doubt. When a match is played without officials, the players are responsible for making decisions, particularly for line calls. There is a subtle difference between player decisions and those of an on-court official. An official impartially resolves a problem involving a call, whereas a player is guided by the unwritten rule that any doubt must be resolved in favor of an opponent. A player in attempting to be scrupulously honest on line calls frequently will keep a ball in play that might have been out or that the player discovers too late was out. Even so, the game is much better played this way.

If that doesn't make it crystal clear, let's look at Section 8:

8. Ball that cannot be called out is good. Any ball that cannot be called out is considered to be good. A player may not claim a let on the basis of not seeing a ball. One of tennis' most infuriating moments occurs after a long hard rally when a player makes a clean placement and an opponent says: "I'm not sure if it was good or out. Let's play a let."Remember, it is each player's responsibility to call all balls landing on, or aimed at, the player's side of the net. If a ball cannot be called out with certainty, it is good. When a player says an opponent's shot was really out but offers to replay the point to give the opponent a break, it seems clear that the player actually doubted that the ball was out.